JPH10137753A - Method for separating and removing selenium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply remove selenium in waste water by allowing a solution contg. selenium compounds and/or their salts to contact with an ion exchange resin or chelate resin, on each of which a reducing substance is supported, to adsorb selenium on the resin. SOLUTION: In this method, a solution contg. selenic acid, selenous acid and/or their salts is allowed to contact with an ion exchange resin or chelate resin, on each of which a reducing substance is supported. As the reducing substance, any reducing substance can be used provided that it can be supported on an ion exchange resin or chelate resin without adversely affecting its reducing power. For example, hydrazine, hydroxylamine, copper(I) ions, or the like can be used as the reducing substance. An adequate amount of such a reducing substance is dissolved into water to allow an aq. solution thus obtained to contact with the ion exchange resin or chelate resin and to support the reducing substance on the resin and then, the solution contg. selenium compounds and/or their salts is allowed to contact with the resulting ion exchange resin or chelate resin at >=70 deg.C to reduce the selenium compounds and/or their salts to metal selenium. Thus, the ion exchange resin or chelate resin, each supporting the reducing substance, has high selenium-removal efficiency and also, can repeatedly be used by repeatedly allowing the resin to contact with the aq. solution of the reducing substance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simple and inexpensive method for separating or removing selenium compounds in water, and for treating water and wastewater belonging to the environmental protection fields such as chemical industry, metallurgy industry and electric / electronic work. It is related to.

[0002]

2. Description of the Related Art Since selenium is harmful, its effluent standards and environmental standards are strictly set at 0.1 ppm and 0.01 ppm, respectively. In order to achieve these standards, there is a long-awaited need in the industry for a resource-saving, energy-saving and efficient selenium separation system. Selenium compounds in water exist mainly in the form of selenous acid, which is tetravalent selenium, and selenic acid, which is hexavalent selenium. Generally, in wastewater treatment of a liquid containing selenium, it is required to remove a small amount of a selenium compound in the presence of a large amount of coexisting salt, but selenium removal in such a situation involves difficulties.

[0003] The difficulty in removing selenium comes from the chemical structure of selenium. Generally, various chelating resins are used for removing a trace amount of heavy metal ions. But,
Chelate resins are used to selectively remove cationic heavy metal ions such as iron and copper, and are not suitable for removing metals such as selenium that exist as oxygen-bound anions. This is because selenic acid and selenous acid have a structure in which oxygen is bonded, and thus it is difficult for the selenium atom to directly interact with other ligands.

Conventionally, methods for removing selenium from wastewater include:
Several methods are known. For example, as a resin for adsorbing selenium, an anion exchange resin such as Eporus K-6 (made by Miyoshi Oil & Fats) is known. Has no effect on the removal of selenium from industrial effluent in which coexisting salts are present. In addition, it has been reported that resins carrying bismuthiol II or azothiophyllin disulfonic acid on anion exchange resins adsorb tetravalent selenium (selenous acid). Not suitable for industrial use. In addition, as described in JP-A-8-132044 and JP-A-8-224585, the method of metallizing and removing selenium by chemical reduction or electrical reduction requires a step of recovering the reduced metal. Therefore, the process becomes complicated.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to easily and inexpensively remove selenium from wastewater in the presence of a high concentration of coexisting salts. Is to provide a way to

[0006]

Means for Solving the Problems The present invention has been accomplished by finding that the above object can be achieved by treating a solution containing a selenium compound or a salt thereof under specific conditions. That is, the present invention provides a method for separating or removing selenium, which comprises contacting a solution containing a selenium compound or a salt thereof with an ion-exchange resin or a chelate resin carrying a reducing substance to adsorb selenium. ,.

When a liquid containing a selenium compound or a salt thereof is brought into direct contact with a reducing substance, selenium can be reduced.
It is necessary to remove the reduced selenium by filtration or the like. Since reduced selenium exists as fine particles, removal by filtration is difficult. Here, if an ion-exchange resin or a chelate resin carrying a reducing substance is used, the reduced selenium compound comes close to the resin, so that selenium is precipitated and adsorbed in the resin. Therefore, there is no need to remove the reduced selenium by filtration or the like. Further, when the reducing substance is supported on the ion exchange resin or the chelate resin, the reducing substance is concentrated on the ion exchange resin or the chelate resin, and the concentration of the reducing substance increases, so that the reaction proceeds easily.

Further, a selenium compound or a selenium compound thereof is used in a state where a reducing substance and an ion exchange resin or a chelate resin are simply mixed in a system without using the ion exchange resin or the chelate resin carrying the reducing substance. When a solution containing salts is brought into contact with them, the reduced selenium does not sufficiently diffuse into the resin, so that selenium is not sufficiently adsorbed in the resin and a part of the selenium exists outside the resin. For this reason, the selenium removal step becomes complicated.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. In the present invention, examples of the solution containing a selenium compound or a salt thereof include a solution of selenic acid, selenous acid or a salt thereof. At this time, the solution contains a selenium compound or a salt thereof and a high concentration of another salt (alkali metal ion, alkaline earth metal ion, chloride ion, sulfate ion, etc.), and the concentration of the selenium compound or a salt thereof is low. May be used. According to the separation or removal method of the present invention, selenium can be separated and removed to the extent that only a trace amount of selenium remains in the treated solution in any of the above solutions.

In the present invention, examples of the ion exchange resin or chelate resin include “functional polymer series chelate resin / ion exchange resin Kodansha Scientific Inc. (issued on August 1, 1986)” and “Diaion Manual Mitsubishi Chemical Corporation”. Known ones, such as those described in "Corporation", can be used without any particular limitation, and either a gel type or a porous type can be used.

As the reducing substance, any reducing substance can be used as long as it can be supported on the above-mentioned ion exchange resin or chelating resin and the reducing property is not impaired.
Specifically, hydrazine, hydroxylamine, copper (I)
Ion, iron (II) ion, tin (II) ion, borohydride compound, sulfite ion, hyposulfite ion, hypophosphite ion and the like. Preferably, hydrazine or hydroxylamine is used. Particularly preferably, hydrazine is used. Further, one kind of the reducing substance may be used alone, or a plurality of reducing substances may coexist.

The loading of the reducing substance on the ion-exchange resin or the chelate resin is performed by combining the ion-exchange resin or the chelate resin with:
An aqueous solution in which an appropriate amount of a reducing substance is dissolved may be brought into contact. For example, when hydrazine or hydroxylamine is used as the reducing substance and a cation exchange resin is used as the carrier, the cation exchange resin adjusted to the H form is
A hydrazine or hydroxylamine solution may be brought into contact.

The selenium compound or its salt can be obtained by contacting the ion-exchange carrier or chelating resin carrying the above-mentioned reducing substance with a solution containing the selenium compound or its salt.
It is reduced to zero-valent metal selenium by the action of the loaded reducing substance. Since the reducing substance is supported by the resin and the reduced selenium is close to the resin, the selenium is precipitated and adsorbed in the resin. In this manner, the selenium compound in the solution can be separated and removed only by passing the solution containing the selenium compound or salts thereof through an ion exchange resin or a chelate resin supporting a reducing substance. As the selenium compound, tetravalent selenium is particularly removed. Where the temperature is
The temperature is preferably 70 ° C. or higher, and at a temperature lower than 70 ° C., the reaction tends to be slow and efficiency tends to be poor. The higher this temperature is, the higher the removal efficiency is, and practically the most preferable temperature is 80 to 95 ° C. Further, the reducing substance consumed in the reduction reaction of selenium loses its activity at that point, but the reducing substance solution can be appropriately brought into contact with the base resin to be supported. Therefore, it can be used any number of times.

The reducing substance carried on the ion-exchange resin or the chelate resin is less expensive than bismuthiol II and azothiophyllin disulfonic acid, which are conventionally known as selenium scavengers, and is suitable for use in wastewater treatment. . In the present invention, the reduction reaction proceeds even in the presence of a coexisting salt, and selenium can be adsorbed and removed.

The separation or removal method of the present invention can be carried out by a batch method or a column method in the same manner as the conventionally known method of separating and adsorbing ions in a solution using an ion exchange resin or a chelate resin. Similarly to the above method, the separation or removal method of the present invention can be effectively used for the treatment of industrial wastewater containing selenium in the chemical industry, metallurgy industry, electricity, electronics industry and the like.

[0016]

【Example】

[Example 1] Hydrazine hydrate 0.15 was added to 10 ml of Diaion SK102 conditioned to H-form (for the method, see "Diaion Manual" (Mitsubishi Chemical)).
g of hydrazine aqueous solution containing 100 g was added and shaken at 25 ° C. for 2 hours in an Erlenmeyer flask. As a result of acid titration of the amount of hydrazine before and after adsorption, the amount of hydrazine carried was 0.3
It was 0 mmol. After filtering this resin and washing with 10 times the amount of water, the resin was further filtered to obtain a hydrazine-supported resin. This resin was fitted with a Dimroth condenser 2
In a 00 ml four-necked flask, add selenous acid 10
100 ml of a ppm solution was added, and the mixture was kept at a reaction temperature of 80 ° C. for 2 hours with stirring. After cooling the liquid, the amount of selenium in the solution is determined by IC
The analysis was performed using a P emission analyzer.

Comparative Example 1 A method similar to that of Example 1 was performed except that H-type Diaion SK102 was used instead of the hydrazine-supported resin in Example 1.

Comparative Example 2 An H-type Diaion SK102 was used in place of the hydrazine-supported resin in Example 1, and the same method as in Example 1 was performed except that the reaction temperature was 25 ° C. Table 1 shows the results of Example 1 and Comparative Examples 1 and 2 together. In the resin supporting hydrazine, the selenium concentration in the solution was decreased, and it is considered that selenite was reduced and adsorbed on the resin.

[0019]

[Table 1]

[Example 2] 10 ppm in Example 1
Instead of 100 ml of selenous acid solution, 100 m of 10 ppm selenous acid solution containing 0.1% by weight of sodium sulfate was used.
The same method as in Example 1 was performed except that l was added.

Example 3 10 ppm in Example 1
A method similar to that of Example 1 was performed, except that 100 ml of a 10 ppm selenite solution containing 1% by weight of sodium sulfate was added instead of 100 ml of the selenous acid solution. Table 2 shows the results of Examples 2 and 3 described above.

[0022]

[Table 2]

[0023]

According to the present invention, there is a remarkable effect that selenium in wastewater can be easily and inexpensively adsorbed, separated and removed even in the presence of a high concentration of coexisting salt. You.

Claims (5)

[Claims] 1. A method for separating or removing selenium, which comprises contacting a solution containing a selenium compound or a salt thereof with an ion-exchange resin or a chelate resin carrying a reducing substance to adsorb selenium. 2. The method according to claim 1, wherein the contacting temperature is 70 ° C. or higher. 3. The method according to claim 1, wherein the reducing substance is hydrazine or hydroxylamine. 4. The method according to claim 1, wherein the selenium compound or a salt thereof is selenous acid or a salt thereof. 5. The method according to claim 1, wherein the solution containing a selenium compound or a salt thereof is an industrial wastewater containing a selenium compound or a salt thereof.